Various means have been devised to simplify the adjustment of axle bearings, specifically, truck axle bearings. It is generally accepted that in some bearing installations, for example, axle bearings, the life of the bearing will be optimized if the adjustment is made for a slight axial compressive deflection, for example, about 0.002 inches (where this amount is the compressive deflection of the two bearings combined), which is often referred to as “a three thousandths preload.” Typical prior art methods of creating these preloads are obtained by applying specified torques to the bearing assembly, for example, by tightening the nut that retains the bearings. However, for several reasons, it is typically extremely difficult to achieve such preload settings under actual in-field conditions, such as in a mechanic shop. For example, the assembly of a heavy truck wheel onto a wheel hub assembly is a relatively cumbersome procedure that hinders the mechanic. Moreover, the wheel hub assembly always includes at least one inner seal, usually a lip type of seal, which can impose a resistive drag torque component to the preload torque, particularly when the seal is new.
Lock nut systems using a single nut are often utilized to retain a wheel or hub assembly, including axle bearings, on a shaft. Such lock nut systems may be connected to a shaft and inhibit rotation of a retaining nut relative to such shafts. For example, such systems are often utilized on motor vehicles, such as axles and wheel ends. Typically, a lock nut will be engageable with a locking member or keeper which inhibits movement of the nut relative to the shaft. The locking member may include a protruding portion which extends into a slot or receiving portion of a shaft. The locking member may also engage the nut such that there is little or no movement between the nut and shaft. After the nut is torqued to its specified amount, the nut is locked to this specified position.
In one example, a user may tighten a nut bolding a bearing on a shaft to a particular torque to achieve the desired preload on the bearing of the wheel hub assembly and then such nut may be loosened to a particular position by referencing an index mark on a face of the nut a particular distance. Such a nut could be turned a particular portion of a rotation by referencing such a marking, e.g., half a turn. Such an adjustment is a particularly inexact procedure given that wheel nut adjustment is desired to have precision of 0.001 of an inch while the degree of rotation of a nut as described is relatively inexact. The loosening of the nut will create an endplay in the bearing and the wheel hub assembly. The amount of endplay depends upon the particular bearing and wheel hub assembly.
Some wheel hub assemblies utilize a spacer located between two bearings mounted on, for example, a spindle of a truck. In such wheel hub assemblies, an inner bearing and outer bearing are mounted on the spindle With such a spacer located therebetween. At least one such wheel hub assembly is utilized by Consolidated Metco, Inc. of Vancouver, Wash., U.S.A. In such assembly, the wheel hub retaining nut which secures the wheel hub assembly is specified by the manufacturer to be torqued to a specified setting. See, Consolidated Metco. Inc. Preset Plus hub install procedures, Part No. 10036676, Copyright 2011. For example, 300 foot pounds for a steer hub and 500 foot pounds for a drive hub or trailer hub. Application of such a torque, as specified by the manufacturer, provides a compressive load on the spacer, e.g., a preload. However, the manufacturer specified torque applied to the retaining nut will often result in an undesireable endplay, for example, one which will reduce the effective life of the wheel bearings. Moreover, in a situation where a spacer other than the OEM specified spacer is used or when a spacer is made to inexact tolerances, the resultant endplay may be undesireable. The manufacturer's desired torque for a retaining nut may typically result in an endplay setting which could vary up to 0.006 inches for the same type spacer due to manufacturing tolerances. Such variance is undesireable because it may lead to premature bearing failure in many beatings.
Thus, a need exists for setting wheel hub assemblies having a spacer therein, for obtaining a desired endplay and increasing bearing wheel life in such assemblies, and for providing more accurate and repeatable procedures for setting and adjusting such wheel hub assemblies.